I f any of you have built IvIark's Flatline compressor, I highly recommend that you use an actual VTL5C3 vactrol in it. I just built one and it works perfect/sounds great. Madbean's 'Afterlife ' is the same circuit and in the instructions document, he specifies to use a VTL5C3 and NOT a home rolled one (although, with a lot of experimentation you probably could).
here's a pic of my built up and tested board:
and here's my slightly rearranged vero of IvIark's so the vactrol would sit flat on the board: